Multiplexer for a piezo ceramic identification device

ABSTRACT

Provided is a Fingerprint sensor using Acoustic Impediography. The sensor includes an Application Specific Integrated Circuit (ASIC or IC) and an array of mechanical resonator used as sensing elements. The array of sensing elements contains multiple sensing elements arranged in rows and columns.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit to U.S. Provisional Application No.61/162,599, filed on Mar. 23, 2009, which is incorporated by referenceherein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a piezoelectricidentification device and applications thereof. More particularly, itrelates to a piezoelectric device for obtaining biometric information,such as a fingerprint, and using the obtained information to recognizeand/or identify an individual.

2. Background Art

Biometrics are a group of technologies that provide a high level ofsecurity. Fingerprint capture and recognition is an important biometrictechnology. Law enforcement, banking, voting, and other industriesincreasingly rely upon fingerprints as a biometric to recognize orverify identity. See, Biometrics Explained, v. 2.0, G. Roethenbaugh,International Computer Society Assn. Carlisle, Pa. 1998, pages 1-34(incorporated herein by reference in its entirety).

Optical fingerprint scanners are available which detect a reflectedoptical image of a fingerprint. To capture a quality image at asufficiently high resolution, optical fingerprint scanners require atminimum optical components (e.g., lenses), an illumination source, andan imaging camera. Such components add to the overall cost of afingerprint scanner. Mechanical structures to maintain alignment alsoincrease manufacturing and maintenance costs.

Solid-state silicon-based transducers are also available in fingerprintscanners sold commercially. Such silicon transducers measurecapacitance. This requires the brittle silicon transducers to be withina few microns of the fingerprint sensing circuit reducing theirdurability. To detect a rolled fingerprint, the sensing array of thesolid-state transducer needs to have an area of 1 inch.times.1 inch anda thickness of about 50 microns. This is a big geometry for silicon thatincreases the base cost of a fingerprint scanner and leads to greatermaintenance costs. Durability and structural integrity are also morelikely to suffer in such a large silicon geometry.

What is needed is an inexpensive, durable fingerprint scanner with lowmaintenance costs. What is also needed is a low cost biometric devicethat can protect individuals and the general populace against physicaldanger, fraud, and theft (especially in the realm of electroniccommerce).

BRIEF SUMMARY OF THE INVENTION

The present invention provides a Fingerprint sensor using AcousticImpediography. The sensor includes an Application Specific IntegratedCircuit (ASIC or IC) and an array of mechanical resonator used assensing elements. The array of sensing elements contains multiplesensing elements arranged in rows and columns.

Further features and advantages of the present invention, as well as thestructure and operation of various embodiments of the present invention,are described in detail below with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate the present invention and, togetherwith the description, further serve to explain the principles of theinvention and to enable a person skilled in the pertinent art to makeand use the invention.

FIG. 1 illustrates a piezoelectric identification device according to anembodiment of the invention.

FIG. 2 illustrates a piezoelectric element according to an embodiment ofthe invention.

FIG. 3 illustrates a row of piezoelectric elements according to anembodiment of the invention.

FIG. 4 illustrates an array of rectangular piezoelectric elementsaccording to an embodiment of the invention.

FIG. 5 illustrates an array of circular piezoelectric elements accordingto an embodiment of the invention.

FIG. 6 illustrates a row of rectangular piezoelectric elements having afill material between elements according to an embodiment of theinvention.

FIGS. 7A and 7B illustrate sensor arrays according to embodiments of theinvention.

FIG. 8 illustrates a more detailed view of the sensor array of FIG. 7A.

FIG. 9 illustrates how the sensor array of FIG. 8 is connected to anapplication specific integrated circuit.

FIG. 10 illustrates how to connect a sensory array to multiplexersaccording to an embodiment of the invention.

FIG. 11 illustrates an identification device according to an embodimentof the invention.

FIG. 12 illustrates circuit components of an identification deviceaccording to an embodiment of the invention.

FIG. 13A illustrates how to apply an input signal to the sensor array ofFIG. 12 and receive an output signal from the sensor array according toan embodiment of the invention.

FIG. 13B illustrates how to control the switches of FIG. 13A accordingto an embodiment of the invention.

FIG. 14 illustrates an example voltage sensing circuit according to anembodiment of the invention.

FIG. 15 illustrates how to minimize cross-talk in a sensor arrayaccording to an embodiment of the invention.

FIG. 16 is a flowchart of a method according to an embodiment of theinvention.

FIG. 17 illustrates using an identification device to obtain biometricinformation according to an embodiment of the invention.

FIG. 18 illustrates an identification device wake-up circuit accordingto an embodiment of the invention.

FIG. 19 illustrates the impedance of a piezoelectric element loaded by afingerprint valley according to an embodiment of the invention.

FIG. 20 illustrates the impedance of a piezoelectric element loaded by afingerprint ridge according to an embodiment of the invention.

FIG. 21 illustrates a sensor array input signal according to anembodiment of the invention.

FIG. 22 illustrates a sensor array output signal according to anembodiment of the invention.

FIG. 23 illustrates how an identification device is used to obtainbiometric information according to an embodiment of the invention.

FIG. 24 illustrates how an identification device is used to obtain abone map according to an embodiment of the invention.

FIG. 25 illustrates a transmitting and/or receiving beam directivityaccording to an embodiment of the invention.

FIG. 26 illustrates how an identification device is used to obtainarteriole blood flow information according to an embodiment of theinvention.

FIG. 27 illustrates a transmitting beam directivity and a receiving beamdirectivity according to an embodiment of the invention.

FIG. 28 illustrates a transmitting and/or receiving beam directivityaccording to an embodiment of the invention.

FIG. 29 illustrates how an identification device is used to obtaincapillary blood flow information according to an embodiment of theinvention.

FIG. 30 illustrates a transmitting and/or receiving beam directivityaccording to an embodiment of the invention.

FIG. 31 is a flowchart of a method according to an embodiment of theinvention.

FIG. 32 illustrates a biometric device according to an embodiment of theinvention.

FIG. 33 illustrates a mobile biometric device according to an embodimentof the invention.

FIG. 34 illustrates a wireless transceiver biometric device according toan embodiment of the invention.

FIG. 35 illustrates a more detailed view of the wireless transceiverbiometric device of FIG. 34.

FIG. 36 illustrates using the wireless transceiver biometric device ofFIG. 34 to complete an electronic sales transaction.

FIG. 37 illustrates various applications for the wireless transceiverbiometric device of FIG. 34.

FIG. 38 illustrates a wireless transceiver biometric device according toan embodiment of the invention.

FIG. 39 is a diagram of an example piconet having coupling BLUETOOTHdevices with a public service layer. Not applicable.

FIG. 40 is a diagram of a sensor array in accordance with the presentinvention.

FIG. 41 is a Matrix of Mechanical Resonator Sensing ElementsInterconnects to ASIC in accordance with the present invention.

FIG. 42 is an illustration of a digit on an Acoustic Impedance digitSensor.

FIG. 43 is a block diagram illustration of ASIC Transmitters.

FIG. 44 is a block diagram illustration of an ASIC Receiver Pipeline.

FIG. 45 is a graphical illustration of the performance of Impedance ofDamped Mechanical Resonator Sensing Elements in accordance with thepresent invention.

FIG. 46 is a graphical illustration of Current through Damped MechanicalResonator Sensing Elements Current through Damped Mechanical ResonatorSensing Elements.

FIG. 47 is a block diagram illustration of an ASIC Receiver PipelineMultiplexer.

FIG. 48 is a block diagram illustration of an ASIC Receiver PipelineMultiplexer Alternative Placement in accordance with the presentinvention.

FIG. 49 is a block diagram illustration of an ASIC Receiver Pipelinewith Sample-and-Hold for increased performance.

FIG. 50 is an illustration of ASIC Receiver Pipeline withSample-And-Hold Generalized.

FIG. 51 is an illustration of Sampling of Sensing Elements on Tx[N−1]and Tx[N] without Sample & Hold in accordance with the presentinvention.

FIG. 52 is an illustration of Sampling of Sensing Elements on Tx[N−1]and Tx[N] with one set of Sample-And-Holds.

DETAILED DESCRIPTION OF THE INVENTION

Overview of the Invention

The present invention relates generally to a piezoelectricidentification device and applications thereof. More particularly, itrelates to a piezoelectric device for obtaining biometric data orinformation, such as a fingerprint, and using the obtained informationto recognize and/or verify the identity of an individual.

Example Devises and Systems According to the Invention

FIG. 1 is a schematic diagram of a piezoelectric identification device110 according to an embodiment of the invention. Identification device100 has a piezoelectric sensor 100, a sensor input signal generator 120,a sensor output signal processor 130, and a memory 140. The input signalgenerated by input signal generator 120 is coupled to sensor 110 by twomultiplexers 150. The output signal of sensor 110 is similarly coupledto output signal processor 130 by two multiplexers 150.

Piezo Ceramic Sensors

Sensor 110 is preferably an array of piezo ceramic elements. Forexample, sensor 110 can comprise an array of polycrystalline ceramicelements that are chemically inert and immune to moisture and otheratmospheric conditions. Polycrystalline ceramics can be manufactured tohave specific desired physical, chemical, and/or piezoelectriccharacteristics. Sensor 110 is not limited to comprising an array ofpiezo ceramic elements, however. Sensor 110 can comprise, for example, apiezoelectric film. A polarized fluoropolymer film, such as,polyvinylidene flouride (PVDF) film or its copolymers can be used.

FIG. 2 illustrates the operating characteristics of a single rectangularpiezo ceramic element 200 having surfaces 210, 220, 230, and 240. Whenforce is applied to surfaces 210 and 220, a voltage proportional to theapplied force is developed between surfaces 210 and 220. When thisoccurs, surfaces 230 and 240 move away from one another. When a voltageis applied to surfaces 210 and 220, surfaces 230 and 240 move towardsone another, and surfaces 210 and 220 move away from one another. Whenan alternating voltage is applied to surfaces 210 and 220, piezo ceramicelement 200 oscillates in a manner that would be known to a personskilled in the relevant art.

FIG. 3 illustrates a row of five rectangular piezo ceramic elements200A, 200B, 200C, 200D, and 200E. Each of these rectangular piezoceramic elements 200 is attached or integral to support 302. Support 302inhibits the movement of one surface of each rectangular piezo ceramicelements 200. Thus, when an alternating voltage is applied to surfaces210 and 220 of piezo ceramic element 200C, a sonic wave is generated atsurface 210 of piezo ceramic element 200C. The frequency of thegenerated sonic wave is dependent on the physical characteristics ofpiezo ceramic element 200C.

FIG. 4 illustrates a two-dimensional array 400 of rectangular piezoceramic elements 200. Array 400 can be made from lead zirconate titanate(PZT). PZT is an inexpensive material. In an embodiment, array 400 issimilar to a PZT 1-3 composite used in medical applications. The piezoceramic elements of sensor 110 according to the invention can haveshapes other than rectangular. As illustrated in FIG. 5, sensor 110 cancomprise an array 500 of circular piezo ceramic elements.

In one embodiment, array 400 can comprise rectangular piezo ceramicelements that are from about 40 microns square by 100 microns deep,thereby yielding a 20 MHz fundamental frequency sonic wave. A spacing of10 microns is used between elements in this embodiment in order toprovide a 50-micron pitch between elements. A pitch of 50-micron enablesan identification device according to the invention to meet the FederalBureau of Investigation's quality standards for fingerprints.

Other embodiments of the invention use geometries different than thepreferred embodiment. For example, a pitch of greater than 50 micronscan be used. Other embodiments also operate at frequencies other than 20MHz. For example, embodiments can operate at frequencies of 30 MHz and40 MHz, in addition to other frequencies.

Also, for example, in another embodiment, array 400 can comprise cuboid(rectangular parallelepiped) piezo ceramic elements that are from about80 square by 220 microns deep. A spacing of about 20 microns is usedbetween elements in this embodiment in order to provide about

In yet another embodiment, array 400 can comprise rectangular piezoceramic elements that are from about 200 microns square by 500 micronsdeep. The cuboids can be modified to prisms or extruded stars, or havechamfered corners or be a to reduce cross talk, facilitate moldingrespectively.

As shown in FIG. 6, the spacing between the elements of a sensor arrayaccording to the invention can be filled-in with a flexible typematerial or filler 602 to suppress any shear waves and give the sensorimproved mechanical characteristics. Micro-spheres 604 can be added tothe filler 602 (e.g., vinyl micro-spheres) to reduce weight and/orincrease the suppression of shear waves. In order to optimize thesignal-to-noise ratio of an identification device, and the devicesensitivity, fillers (e.g., araldite filled with air filled vinylmicro-spheres) that provide high acoustical attenuating and electricalisolation should be used.

At least four fabrication methods exist for producing array 400. Thesemethods include: laser cutting, dicing, molding, and screen-printing.Laser cutting involves using an excimer laser to cut small groves andthereby form the elements of array 400. Dicing involves using highperformance dicing equipment to form groves and the elements of array400. Molding involves using injection molding equipment to form array400. Screen-printing is a technique similar to that of solder printingin the assembly of printed circuit boards, where highly automated screenprinting machines are adapted with laser cut stencils. This method isparticularly suited to producing 20 MHz sonic wave elements since theceramic elements are only 100 microns thick.

This method involves producing a ceramic slurry of appropriateconsistency, and has the advantage of not requiring surface grinding asmay be required with the molding method.

FIG. 7A illustrates a sensor array 700 comprising rectangular piezoceramic elements according to a preferred embodiment of the invention.Sensor array 700 is a multi-layer structure that includes atwo-dimensional array of rectangular piezo ceramic elements 200, similarto array 400. Conductors (such as conductors 706 and 708) are connectedto each of the rectangular piezo ceramic elements 200. The conductorsconnected to one end of each element 200 (e.g., conductor 706) areoriented orthogonal with respect to the conductors connected to anotherend of each element 200 (e.g., conductor 708). A shield layer 702 can beadded to one side to provide a protective coating where a finger can beplaced proximate to sensor array 700. A support 704 can be attached tothe opposite end of the sensor array. Sensor array 700 is described inmore detail below.

Piezo Film Sensors

FIG. 7B illustrates a sensor array 750 comprising piezoelectric film(piezo film) according to an embodiment of the invention. FIG. 7B is across-sectional view of sensor array 750. Sensor array 750 is amulti-layer structure that includes a piezoelectric layer 752 sandwichedby two conductor grids 754 and 756. Conductor grids 754 and 756 eachconsist of rows of parallel electrically conductive lines. Preferably,the lines of grid 754 are oriented orthogonal with respect to the linesof grid 756 (that is, in x and y directions, respectively). Thisorientation creates a plurality of individually addressable regions orelements in the piezo film. As used herein, the term element refers toany region of a sensor array that can be addressed, either individuallyor as part of a larger region, using the rows of parallel electricallyconductive lines (conductors). Piezoelectric polymer film sensors arefurther described in Piezo Film Sensors: Technical Manual, availablefrom Measurement Specialities, Inc. Norristown, Pa. Apr. 2, 1999 REVB(incorporated by reference herein in its entirety).

Shield layer 758 can be added to one side where a finger is placed toprovide a protective coating. Foam substrate 760 can be used as asupport. As shown in FIG. 7B, the multiple layers of sensor array 750are stacked along one direction (e.g., a z-direction).

In an embodiment, piezo layer 752 is a polarized fluoropolymer film,such as, polyvinylidene flouride (PVDF) film or its copolymers.Conductor grids 754 and 756 are silver ink electrodes printed onopposite sides of the PVDF film 752. Shield layer 758 is made ofurethane or other plastic. Foam substrate 760 is made of TEFLON. Anadhesive 762, 764 holds shield layer 758 and foam substrate 760 onopposite sides of the printed PVDF film 752 as shown in FIG. 7B.

In an embodiment, the PVDF film, including the printed electrodes, canbe peeled off like a label for easy replacement. As shown in FIG. 7B,sensor array 750 can be mounted by adhesive 766 onto wax paper or othermaterial (not shown) for easy peel off. This allows the piezo sensor tobe installed and/or replaced simply and easily at minimum cost. Comparedto optical and silicon technologies, maintenance of the piezo sensorarray 750 is trivial.

Sensor Array Address Lines

FIG. 8 illustrates a more detailed view of sensor array 700. Asdescribed above, sensor array 700 comprises piezo ceramic elementshaving an filler 602. Filler 602 preferably contains micro-spheres 604.This structure is then sandwiched between several layers. This centralcomposite layer is an active structure that can be used, for example, tomap fingerprint mechanical impedances into a matrix of electricalimpedance values.

Each rectangular piezo ceramic element 200 of sensor array 700 isconnected to two electrode lines (e.g., conductors 706 and 708). Theelectrode lines on one end of sensor array 700 run perpendicular to theelectrode lines on opposite end of sensor array 700. Thus, any singleelement 200 of the array can be addressed by selecting the two electrodelines connected to it. The electrode lines are preferably created byvacuum despoliation and lithography, and they are connected to theswitching electronics via an interconnect technique described below.

On top of the one set of electrode lines is a protection layer 702.Protective layer 702 is preferably made of urethane. This protectinglayer 702 is intended to be in contact with a finger during operation ofthe sensor.

A support 704 or backing layer serves as a rear acoustical impedance foreach of the rectangular piezo ceramic elements 200. In a preferredembodiment, support 704 is made of TEFLON foam. In order to provide alarge variation of the electrical impedance of an element when loadedand unloaded, the acoustical impedance support 704 should beacoustically mismatched to the sensor element material. Either a verylow or a very high acoustic impedance material can be used. Forembodiments using piezo ceramic materials, the preferred impedancemismatch can be obtained by an air backing rather than by a hardbacking. This is because the sensor has a high acoustic impedance.

The materials described herein for constructing sensor array 700 areillustrative and not intended to limit the present invention. Othermaterials can be used, as would be known to a person skilled in therelevant art.

FIG. 9 illustrates how sensor array 700 can be connected to anapplication specific integrated circuit. As described herein, anindividual piezo ceramic element (m, n) of sensor array 700 can beaddressed by selecting (addressing) conductor m on the top of sensorarray 700 and conductor n on the bottom of sensor array 700. Otherconductors can be either grounded or open (high impedance state),particularly those conductors used to address elements in theneighborhood of the element being selected, in order to reducecross-talk. Parasitic currents in the neighborhood of the selectedelement are minimized mechanically by the interstitial filler 602,described above with regard to FIGS. 6 and 7A. Since in one embodiment,the spacing between elements (pitch) is about 50 microns and standardbonding technologies require a pitch of about 100 microns, alternaterows on an “East” and “West” and alternate columns on a “North” and“South” sides of sensor array 700, as shown in FIG. 9, connect thesensor to the “outside world”. As shown in FIG. 9, These conductors canbe terminate in a “Bump” technology around three edges 908 of an ASICmultiplexer 902. In an embodiment, side 908 of ASIC multiplexer 902 isabout 3 mm.

In an embodiment, ASIC multiplexer 902 is connected to a high densityflex 906. High density flex 906 is connected to an epoxy substrate 904.Conductors can be formed or attached to the high flex to couple theconductors of the array to ASIC multiplexer 902. For example, aconductor on high density flex 906 is shown in FIG. 9 coupling conductor708 to ASIC multiplexer 902. Conductor is coupled to ASIC multiplexer902 by bump soldering. Anisotropic glue can be used to couple theconductor on high density flex 906 to conductor 708 of the sensor array.Other means for connecting and electrically coupling ASIC multiplexer902 to sensor array 700 are known to persons skilled in the relevantart, and these means also can be used in accordance with the invention.

FIG. 10 illustrates how to connect a sensory array 1002 to four ASICmultiplexers 902 according to an embodiment of the invention. Asdescribed herein, electrode lines or conductors can be vapor depositedon both sides of the substrate 902 (not shown in FIG. 10) and thenetched into the desired pattern. Before the line and row pattern isetched, substrate 902 should be polarized in a manner similar to that ofmedical transducers.

A polarized substrate is connected to a socket or multi chip module casethat is compatible with available printed circuit board technologies.The piezo ceramic matrix or sensor array 1002 can be backed by an airequivalent foam or aluminum oxide. Either backing is designed tomiss-match the composite piezo material at 8 Mrayls to cause any energycoupling to occur only at the front face of sensor array 1002, where forexample a fingerprint can be scanned. It should be noted in FIG. 10 thatthe conductors on both the top and bottom of sensor array 1002 areinterleaved in the manners described above to facilitate bondingtechnologies requiring a pitch of about 100 microns.

FIG. 11 illustrates an identification device 1100 according to anembodiment of the invention. In a preferred embodiment, device 1100 hasa piezo ceramic sensor array 1102 that is physically lager enough tocapture any fingerprint placed without accuracy on sensor array 1102(e.g., about 25 mm square). Sensor array 1102 is preferably compliantwith CJIS ANSII NIST standards in resolution (500 points per 25.4 mm),and it has a pixel dynamic range sufficient to provide 256 distinctshades of gray.

As show in FIG. 11, in an embodiment, substrate 1110 is attached to aprinted circuit board 1104. The conductors of sensor array 1102 arecoupled to two integrated circuits 1106 and two integrated circuits1108, which couple sensor array 1102 to other circuits, which aredescribed elsewhere herein. Integrated circuit 1112 is a wirelesstransceiver that enables embodiments of the invention to communicatewith other devices as part of a personal area network. This connectivitypermits embodiments of the invention to supply, for example, a standardsecure identification and/or authorization token to any process ortransactions that need or require it. The connection scheme shown isFIG. 11 is an alternative connection scheme that can be used toimplement embodiments of the invention.

The above sensor array descriptions are illustrative and not intended tolimit the present invention. For example, piezo layer 752 can be anymaterial exhibiting a piezoelectric effect including, but not limitedto, piezoelectric polymers. Conductor grids 706, 708, 754 and 756 can beany electrically conductive material including, but not limited to,metals. Likewise, other types of protective material can be used forshield layers 702 and 758 as would be apparent to a person skilled inthe art given this description. Other types of supportive material canbe used in place of support 704 or foam substrate 760.

Example Identification Device

FIG. 12 illustrates an identification device 1200 according to anembodiment of the invention. Device 1200 comprises an input signalgenerator 1202, a sensory array 1220, an output signal processor 1240, amemory controller 1260, and a memory 1270. Sensor array 1220 is coupledto input signal generator 1202 and output signal processor 1240 bymultiplexers 1225A and 1225B, respectively. A controller 1230 controlsthe operation of multiplexers 1225A and 1225B. The operation ofidentification device 1200 is further described below.

In an embodiment, input signal generator 1202 comprises an input signalgenerator or oscillator 1204, an variable amplifier 1206, and a switch1208. In one embodiment, oscillator 1204 produces a 20 MHz signal, whichis amplified to either a low or a high voltage (e.g., about 4 volts or 8volts) by variable amplifier 1206, depending on the mode in which device1200 is operating. Switch 1208 is used to provide either no inputsignal, a pulsed input signal, or a continuous wave input signal. Switch1208 is controlled to produce the various types of input signalsdescribed herein in a manner that would be known to a person skilled inthe relevant art. As shown in FIG. 12, the input signal generated byinput signal generator 1202 is provided to sensor array 1220, throughmultiplexer 1225A, and to controller 1230 and output signal processor1240.

The structure and details of sensor array 1220 are explained above. In apreferred embodiment, sensor array 1220 is a piezo ceramic composite ofrectangular elements designed to operate with a 20 MHz input signal.

Example Multiplexer

FIGS. 13A and 13B illustrate how to apply an input signal generated byinput signal generator 1202 to the sensor array 1220, and how to receivean output signal from sensor array 1220 according to an embodiment ofthe invention. In one embodiment, sensor array 1220 comprises 200,000elements 200 arranged in a two-dimensional array (i.e., a 500.times.400element array). The 500 conductors of array 1220 that connect, forexample, to the element rows on the bottom of array 1220 must beconnected to input signal generator 1202, either one at a time or invarious groupings, while the 400 lines that connect to the columns onthe top of the array 1220 must be connected, for example, to animpedance meter or Doppler circuit, either one at a time or in variousgroups. This task is accomplished by multiplexers 1225.

In another embodiment, the sensor array 1220 can include about 25,000 toabout 64,000 elements 200 (e.g., with 80.times.80.times.200 micronelements). Yet another embodiment can include about 16,000 elements 200(e.g., with 200.times.200.times.500 micron elements).

In an embodiment, multiplexers 1225 are incorporated into four identicalASICs (see FIG. 10). These four ASICs comprise analog multiplexers,amplifiers, detection circuits, and logic. In a preferred embodiment,the voltage of the input signal to sensor array 1220 is restricted toless than 8 volts, which permits the ASICs to be constructed using3-micron geometry, and to attain a switch impedance of less than 5 ohms.The four basic sections of each of these ASIC are: (1) multiplexers asdescribed herein; (2) amplifier/automatic gain controllers; (3) Dopplerdetectors; and (4) a digital signal processor (DSP) interface. Thestructure and implementation of items (2) through (4) are known topersons skilled in the relevant art.

In an embodiment, multiplexers 1225 comprise seventeen 16:1multiplexers, thus giving one output or 16 outputs as selected. Thefunction of each switch in the multiplexer is determined by a shiftregister 1302 that is 272 bits long and 2 bits wide (see FIG. 13B). Theloading and clocking of shift register 1302 is performed by controller1230, which comprises a counter and logic that would be known to aperson skilled in the relevant art. As shown in FIG. 13A, the conductorsof sensor array 1220 can be connected to either ground, signal inputgenerator 1202, or they can be unconnected (high impedance). Multiplexer1225A is designed for lowest “on” resistance. Multiplexer 1225B connectsall (256) conductors of one side of sensor array 1220 to one or sixteensense nodes. Both multiplexers 1225A and 1225B are connected to the samefunction logic (i.e, controller 1230) so that the proper sensor elementsare selected and used, for example, for voltage sensing. Element columnsand rows, in the neighborhood of an element or group of elementsselected for sensing, can be switched to ground to prevent coupling andinterference.

FIG. 13B illustrates how to control the switches of multiplexers 1225according to an embodiment of the invention. As described herein, eachswitch of multiplexer 1225 connected to a conductor of array 1220 can bein one of three states: connected to ground, connected to signal inputgenerator 1202, or open (high impedance). This can be implemented, forexample, using two CMOS gates, as shown in FIG. 14. A 272 bit long by 2bit wide shift register can then be used to control the position of eachswitch. Bits from controller 1230 are shifted into shift register 1302to control the position of the switches of multiplexers 1225. In anembodiment, shift register 1302 is coupled to the switches ofmultiplexer 1225 using latches so that the position of the multiplexerswitches remain constant as new bits are being shifted into shiftregister 1302. How to implement this embodiment would be known to aperson skilled in the relevant art. Other means for implementing thefunctionality of multiplexers 1225 can be used without departing fromthe scope of the invention.

FIG. 14 illustrates an example voltage detector 1244 according to anembodiment of the invention. As will be understood by a person skilledin the relevant art, the voltage drop in each conductor of sensor array1220 is large compared to the voltage drop of the elements of the arraybecause all the elements coupled to a particular conductor are drawingfrom a signal source (i.e., input signal generator 1202). If eachelement has an impedance of 500 ohms, the impedance of 400 elementsconnected in parallel is 1.25 ohms. This situation can be compensatedfor, however, by using a second multiplexer to measure the true outputvoltage of the elements. As can be see in FIG. 14, multiplexer 1402 isused to move the virtual zero-point of the amplifier 1404 before theswitch of multiplexer 1406.

As explained herein, the choice of apertures, their relative position insensor array 1220, and the number of apertures intended to be operatedsimultaneously will affect the complexity of the logic of formultiplexer 1225. Thus, in a preferred embodiment, this logic isimplemented using a DSP. The mode of operation of device 1200 can beselected on the four identical ASICs described above using modeswitches. These mode switches can be used to operate switches 1250 (seeFIG. 12) to direct the output of multiplexer 1225 B to the properdetector of output signal processor 1240.

The operation of impedance detector 1242, signal time of travel detector1246, and Doppler shift detector 1248 are described below. Circuits toimplement the functionality of these detectors will be known to personsskilled in the relevant art given their descriptions herein.

The output of output signal processor 1240 is biometric data. This datacan be stored in memory 1270 using memory controller 1260. FIG. 21 is aflowchart of a method according to an embodiment of the invention. Useof this biometric data is described below.

FIG. 15 illustrates means for increasing scanning speed and minimizingcross-talk in a sensor array 1500 according to an embodiment of theinvention. As seen in FIG. 15, multiple elements can be activesimultaneously and a first means for minimizing cross-talk is toseparate geographically the active elements 1502 of array 1500. Asexplained herein, a dynamic grounding scheme (i.e., coupling theelements 1504 in the neighborhood of an active element 1502 to ground)can be used that moves with the active elements 1502 as they scan acrossthe sensor array 1500. This reduces the capacitive coupling to groundand electrical cross-talk while maintaining a Faraday Cage for allsensed frequencies. In addition, an interstitial filler can be used toreduce cross-talk and thereby the parasitic currents in the neighborhoodof the selected elements 1502. Other elements of array 1500, e.g.,elements 1506, are connected to conductors that are open.

Example Method Embodiments of the Invention

FIG. 16 is a flowchart of a method 1600 according to an embodiment ofthe invention. Method 1600 comprise two steps 1610 and 1620. In step1610, a biological object, for example, a finger or a hand, is placeproximate to a piezoelectric ceramic array. In step 1620, an output isobtained from the sensor array. The obtained output is processed asexplained below to obtain biometric data that can be used to recognizeor verify the identity of a person, whose finger or hand, for example,was placed proximate to the sensor array.

Each of the steps 1610 and 1620 are described further below with regardto the various operating modes of device 1200, described above.

As described herein, identification device 1200 is operated in differentmodes depending on the biometric data to be obtained. The biometric datathat can be obtained using device 1200 includes fingerprints, bone maps,arteriole blood flow, and/or capillary blood flow.

FIG. 17 illustrates using identification device 1200 to obtain afingerprint of a finger according to an embodiment of the invention. Asseen in FIG. 17, finger 1702 is place proximate to the sensor array 1220of device 1200. In a preferred embodiment, sensor array 1220 is similarto piezo ceramic sensor array 700.

Two fingerprint ridges 1704 of finger 1702 are in direct contact withprotective shield 702. A fingerprint valley (i.e., cavity) 1706 offinger 1702 is not in direct contact with protective shield 702. As canbe seen in FIG. 17, there are approximately six piezo ceramic elements200 between the adjacent fingerprint ridges 1704.

Initially, device 1200 is in a power saving mode. This mode isparticularly useful for prolonging battery life in mobile versions ofdevice 1200. When finger 1702 applies a force to sensor array 1220, awake-up circuit 1800 (see FIG. 18) operates to turn-on device 1200.

Wake-up circuit 1800 comprises a capacitor 1802, a diode 1804, and aswitch 1806. When finger 1702 applies a force to piezo ceramic elements200, a voltage is developed by the elements causing capacitor 1802 toaccumulate a charge. When enough charges has been accumulated, thevoltage so produced causes switch 1806 to be turned-on. Voltage source1808 is used to power device 1200 once switch 1806 is turned-on. Powerwill continue to be supplied to device 1200 until capacitor 1802 isdischarged using a turn-off circuit (discharging resister not shown).

After device 1200 wakes-up, device 1200 can be operated in either animpedance detection mode or an attenuation mode (voltage mode) in orderto obtain an output from sensor array 1220 that can be processed toobtain the fingerprint of finger 1702. Each of these modes are explainedbelow.

The outputs of the elements of piezo sensor 200 can be summed todetermine the centroid of the point of contact of the finger with thedevice. Any movement of the finger across the device can thus be sensedand the sensor 200 can be used as a pointing device. For example, thecentroid of a finger in contact with piezo sensor 200 can be used topoint on interconnected viewing devices. The sum of the sensors elementscan also used to determine if the user is pressing with too little ortwo much force and the result fed back to the user.

The embodiment shown in FIG. 18 can also be used as a switch to make aselection on an interconnected viewing device. For example, if ananalog-to-digital converter (not shown) is coupled to capacitor 1802,the voltage across capacitor 1802 is converted to a digital signal thatcan be used interactively to make the selection by a user. As a uservaries the pressure applied to sensor 200, the voltage across capacitor1802 will vary. The analog-to-digital converter converts this timevarying voltage, for example, to a series of numbers between 00000000(base 2) and 11111111 (base 2). The output of the analog-to-digitalconverter is periodically sampled and used to make and/or indicate aselection (e.g., the number can be input to a processor and used to makeand/or indicate a particular selection). A graphical user interface on aviewing device provides feedback to the user and indicates to the userwhich of the possible selections is being selected by the user based onthe pressure applied to sensor 200. To change a selection, the usersimply applies either more or less pressure to sensor 200.

Impedance Mode

FIG. 19 illustrates the impedance of a single piezo ceramic element 200loaded by a fingerprint valley 1706 according to an embodiment of theinvention. At a frequency of about 19.8 MHz, the impedance of an element200 loaded by a fingerprint valley is approximately 800 ohms. At afrequency of 20.2 MHz, the impedance is approximately 80,000 ohms. At afrequency of 20 MHz, the impedance is approximately 40,000 ohms. As canbe seen when FIG. 19 is compared to FIG. 20, both the absolute impedanceof an element 200 loaded with a fingerprint valley and the change inimpedance with frequency of an element 200 loaded with a fingerprintvalley is significantly different from that of an element 200 loadedwith a fingerprint ridge. This difference can be used to obtain anoutput from sensor array 1220 that can be processed by output signalprocessor 1240 to produce fingerprint data.

FIG. 20 illustrates the impedance of a single piezo ceramic element 200loaded by a fingerprint ridge 1704 according to an embodiment of theinvention. As can be seen in FIG. 20, at a frequency of about 19.8 MHz,the impedance of an element 200 loaded by a fingerprint ridge isapproximately 2,000 ohms. At a frequency of 20.2 MHz, the impedance isapproximately 40,000 ohms. At a frequency of 20 MHz, the impedance isapproximately 20,000 ohms. Thus, both the absolute impedance of anelement 200 loaded with a fingerprint ridge and the change in impedancewith frequency of an element 200 loaded with a fingerprint ridge issignificantly different from that of an element 200 loaded with afingerprint valley.

When operating in the impedance mode, identification device 1200determines the absolute impedance of an element 200 and/or the change inimpedance of an element 200 with frequency to determine whether a givenelement 200 is loaded by a fingerprint ridge 1704 or a fingerprintvalley (cavity) 1706. To obtain a measure of the impedance of an element200, input signal generator 1202 is used to produce low voltage pulsesthat are input to the elements of sensor array 1220 using multiplexer1225A.

The output signals obtained at multiplexer 1225B are related to theabsolute impedance of the elements 200 of array 1220. These outputsignals are routed by switch 1250 to impedance detector 1242 todetermine a measure of the absolute impedances of the elements of array1220. To obtain a fingerprint, it is only necessary that impedancedetector 1242 be able to determine whether a given element 200 is loadedby a fingerprint ridge or a fingerprint valley. These determinations ofwhether a particular element 200 is loaded by a fingerprint ridge orfingerprint valley can be used to generate pixel data that representsthe fingerprint of finger 1702. The fingerprint is stored in memory1270. The fingerprint can also be transmitter to other devices asdescribed below.

If the fingerprint of finger 1702 is scanned twice using two differentinput signal frequencies, the change in the impedances of the elements200 with frequency can be calculated. As already described herein, thechange in the impedances of the elements 200 with frequency is differentdepending on whether an element 200 is loaded by a fingerprint ridge orfingerprint valley. As can be seen in FIG. 12, the input signalgenerated by input signal generator 1202 is supplied to output signalprocessor 1240. Thus, output processor 1240 can determine both thefrequency and the voltage of the signals being input to sensor array1220.

An impedance detector circuit (not shown) can be implemented using an opamp. The output of multiplexer 1225B is supplied to the negative port ofthe op amp and an amplified signal is obtained at the output port. Aswould be known to a person skilled in the relevant art, the positiveport of the op amp is coupled to ground and a resistance is placedbetween the negative port and the output port of the op amp.

If the amplified voltage at the output port exceeds a predeterminedthreshold voltage, the particular element 200 being measured is loadedby a fingerprint ridge. This is due to the fact that the absoluteimpedance of an element 200 loaded by a fingerprint ridge (for a givenfrequency) is approximately half of the impedance of an element 200loaded by a finger print valley. Thus, the voltage of the output signalprovided to the op amp from an element 200 loaded by a fingerprint ridgeis approximately twice the voltage of the output signal provided to theop amp from an element 200 loaded by a fingerprint valley.

In general, slightly different processing techniques can be used inassociation with smaller piezo ceramic sensor arrays (e.g., less thanabout 100,00 elements) that include larger individual elements (e.g.,greater than about 40 microns by 100 microns). For example, an exemplarypiezo ceramic element can be comprised of a capacitor having PZT as thedielectric. The permitivity of PZT can be relatively high (e.g., above1500 (coulombs/volt-meter).

At 1500, the piezo electric effect causes the capacitor to mechanicallyexpand or contract under a voltage. At various frequencies, the elementwill exhibit preferential oscillation or clamping based on theinteraction of the wavelength, the speed of sound in the element, andthe physical dimensions of the element. The most useful oscillations arethe series resonance and parallel resonances which are at 7.6 and 8.3MHz for in one exemplary embodiment. An expected exponential lowering ofthe impedance of a capacitor, with increasing frequency, has deviationsat these two frequencies, as energy is or is not consumed.

It has been discovered that the point spread fiction of mechanicalcoupling to a fingerprint ridge is offset for the parallel resonance.This concept facilitates spatial sampling frequencies of up to fourtimes the spatial element frequency. Additionally, the sensitivity to aridge or valley is very biased as a valley causes no transfer of energy.A ridge, however, will be insonified and a distant valley can bedetected through the ridge. The net result is that the a sensor candetect valleys better than ridges and the valleys can be much smallerthan the element pitch.

Attenuation/Voltage Mode

As stated above, device 1200 can also operate in an attenuation orvoltage mode to obtain the fingerprint of finger 1702. This mode ofoperation is available whether sensor array 1220 is a piezo ceramicarray (e.g., array 700) or a piezo film array (e.g., array 750). Theattenuation mode of device 1200 is based on the principle that energyimparted to an element 200 loaded by a fingerprint ridge 1704 can betransferred to finger 1702, while energy imparted to an element 200loaded by a fingerprint valley 1706 cannot be transferred to finger1702.

In the attenuation mode, input signal generator 1202 produces a highvoltage, pulsed signal that is provided to the elements of sensor array1220 using multiplexer 1225A. FIG. 21 illustrates a one-cycle inputpulse. An input signal is typically longer than one-cycle, however. Inan embodiment, an input signal is about ten-cycles long. These inputsignal causes the elements of the array to vibrate and produce sonicwaves. These sonic waves can travel from an element through the shieldlayer to a fingerprint ridge 1704 above the element. These sonic wavescan pass into a fingerprint ridge 1704 because the acoustic impedance ofthe shield layer is matched to the acoustic impedance of finger 1702. Noacoustic barrier to the sonic waves is formed by the interface between afingerprint ridge 1704 and the shield layer. The energy imparted to anelement loaded by a fingerprint ridge is thus dissipated. In the case ofan element loaded by a fingerprint valley, the energy imparted to anelement remains trapped in the element for a longer period of time. Thisis because the air in the fingerprint valley acts as an acousticbarrier.

After a number of cycles, the voltages of output signals obtained forthe array are determined and processed to obtain the fingerprint offinger 1702. FIG. 22 illustrates an example output signal. In anembodiment, since the energy imparted to an element loaded by afingerprint ridge 1704 is dissipated more quickly that then energyimparted to an element loaded by a fingerprint valley 1706, the voltageof an output signal obtained from an element loaded by a fingerprintridge 1704 is only about 1/10th of the voltage of the input signal. Inthis embodiment, the voltage of an output signal obtained from anelement loaded by a fingerprint valley 1706 is about ½ of the voltage ofthe input signal. This difference in voltages can be detected by voltagedetector 1244 and processed to generate the fingerprint of finger 1702.A means for implementing voltage detector 1244 is described above. Othermeans will be known to a person skilled in the relevant art.

Doppler-Shift and Echo Modes

Identification device 1200 can be operated in at least two other modes.These modes are signal time of travel (echo) mode and Doppler-shiftmode. Echo mode can also be referred to as imaging mode. These modes areused to obtain biometric data such as bone maps, arteriole-veinal maps,arteriole blood flow and capillary blood flow, as described below.Combinations of these biometrics and/or others can also be obtained. Forexample, a ratio of arteriole blood flow to capillary blood flow can beobtained and used to indicate the emotional state or well-being of ahost.

FIG. 23 illustrates how an identification device 1200 operating in echoor Doppler-shift mode can be used to obtain biometric informationaccording to embodiments of the invention. As described herein, a highvoltage signal can be input to the elements of sensor array 1220 toproduce sonic waves. These sonic waves travel through finger 1702 andare reflected by various features of finger 1702, such as, for examplethe bone of finger 1702, the fingernail of finger 1702, or the bloodflowing in finger 1702.

FIG. 24 illustrates how an identification device 1200 is used to obtaina three-dimensional bone map according to an embodiment of theinvention. To generate a map of a bone 2402 of finger 1702, device 1200is operated in its echo mode. Sound waves traveling from the skinsurface into finger 1702 will be reflected from the bone structure ofbone 2402. This structure can be identified from the large echoamplitude that it causes. Since the echo travel time is a measure of thesensor to bone distance, a three-dimensional map of the shape of bone2402 can be attained.

To obtain a map of bone 2402, a high voltage, pulsed input signal isgenerated by input signal generator 1202 and provided to the elements ofarray 1220. This input signal causes the elements to generate sonicwaves that travel into finger 1702. As shown in FIG. 24, only certainelements 200 of array 1220 are actively generating sonic waves at anygiven time. In accordance with the invention, and as described herein,active sonic wave transmitting and receiving apertures are configuredand moved (scanned) across sensor array 1220 using controller 1230 andmultiplexers 1225. The generated sonic waves travel through finger 1702and are reflected by the structure of bone 2402. These reflected sonicwaves are then detected by the receiving apertures. The time of travelof the sonic waves are obtained by detector 1246 of device 1200 and usedto detect whether bone structure is located at a various distances fromarray 1220. As would be known to a person skilled in the relevant art,this mode of operation is similar to how radars operate.

The wavelength of the sonic waves and the aperture selected define thetransmit and receive beam shape. Various aperture sizes and beamdirectivity can be formed in accordance with the invention. FIG. 25illustrates a example beam directivity that can be used to obtain a bonemap of bone 2402 according to an embodiment of the invention. Otherbeams can also be used.

FIG. 26 illustrates how identification device 1200 is used to obtainarteriole blood flow information according to an embodiment of theinvention. An artery 2602 and capillaries 2604 are shown for finger1702. As seen in FIG. 26, arteriole blood flow is parallel to thesurface of sensory array 1220.

Arteriole blood flow data is obtained from device 1200 while it isoperating in Doppler-shift mode. To receive a Doppler-shift signalback-scattered from red blood cells flowing in artery 2602, the transmitand receive directivity beam patterns of sensor array 1220 must form oneor more overlapping volumes 2606.

FIG. 27 illustrates a transmitting aperture 2610A and a receivingaperture 2610B according to an embodiment of the invention that form anoverlapping volume 2606. One approach for creating transmittingapertures 2610A and receiving apertures 2610B is to make the aperturesless than about six wavelengths square (e.g., 300 microns or sixelements on a side) and spaced at a pitch of two wavelengths (600microns). These apertures create side beams or grating lobes at about 30degrees and form overlapping regions 2606 at a depth appropriate fordetecting arteriole blood flow. FIG. 28 illustrates a transmittingand/or receiving beam formed by such apertures according to anembodiment of the invention. Other apertures can also be used. The angleat which grating lobes can be created are controlled by the ratio of thepitch between apertures and the wavelength of the sonic waves generated,as would be known to a person skilled in the relevant art given thedescription of the invention herein.

As seen in FIGS. 26 and 27, sonic energy produced by aperture 2610A isscattered by blood cells flowing in artery 2602 and received at aperture2610B. The input signal provided to the elements of array 1220 that makeup aperture 2610A is a high voltage, continuous wave signal. This inputsignal is also provided to output signal processor 1240 as a referencesignal for Doppler-shift detector 1248. This input or reference signalis mixed by Doppler-shift detector 1248 with the output signal receivedfrom aperture 2610B to obtain Doppler-shift information. Circuits forimplementing Doppler-shift detector 1248 are known in the relevant art,and thus not reproduced here.

FIG. 29 illustrates how an identification device 1200 is used to obtaincapillary blood flow information according to an embodiment of theinvention. As seen in FIG. 29, capillary blood flow is in a directionnormal to the surface of sensor array 1220. To separate the capillaryflow from the arteriole flow, multiple apertures of nine elements(3.times.3, 150 micron square) can be selected. This aperture willcreate a very small and close area of sensitivity that can be replicatedin many parts of sensor 1220 simultaneously. The sensitivity of theapertures can be increased by adding the Doppler signals of multipleapertures together. The sensitivity apertures is focused in the firsthalf millimeter of finger 1702 closest to the surface of array 1220.FIG. 30 illustrates a transmitting and/or receiving beam directivitythat can be used to detect capillary blood flow according to anembodiment of the invention.

When using device 1200 to detect blood flow, using a pulsed Dopplerembodiment has the advantage of having the same aperture perform boththe transmit and receive functions. In addition, by gating the receivedsignal, only back-scattered information resulting from a well-definedsample volume is analyzed to obtain the blood flow pattern.

FIG. 31 is a flowchart of a more detailed method 3100 for obtainingbiometric data using device 1200. Method 3100 is described withreference to a particular embodiment of device 1200 having a piezo filmsensor array.

In step 3102, device 1200 is awakened and piezo film sensor array 1220is switched to detect an initial pixel or a group of pixels. Controller1230 switches multiplexers 1225A and 1225B to a designated initial pixelor group of pixels. In one example, piezo film sensor array 1220 is a512.times.512 pixel array. Multiplexers 1225A and 1225B are each used toaddressed and/or select a particular grid line (conductor) at adesignated address of the initial pixel or group of pixels beingdetected.

In step 3104, an input signal is applied to piezo film array 1220. Apulse is applied in one 30 MHZ cycle. Oscillator 1204 generates anoscillation signal at 30 MHZ. Multiplexer 1225A forwards the input pulseto an initial pixel or group of pixels. This input signal is also sentto controller 1230 and output signal processor 1240.

In step 3106, an output signal is obtained from piezo film array 1220.Output signal processor 1240 waits a number of cycles before detecting asignal at the pixel. For example, in response to the signal sent frominput signal generator 1202, output signal processor 1240 waits a numberof cycles after the input pulse is applied to the pixel (or group ofpixels). In step 3108, when the wait is complete, a voltage, forexample, is evaluated using voltage detector 1244.

For example, one 30 MHZ cycle corresponds to approximately 33nanoseconds. The wait can be approximately 5 cycles or 150 nanoseconds.Other wait durations (e.g. a greater or smaller number of periods) canbe used depending upon the oscillator frequency and/or other designconsiderations. This wait allows the ring down oscillation due to thepresence of a fingerprint ridge to occur, in response to the appliedelectrical pulse at the pixel, as described above.

In step 3108, a filtered voltage is evaluated by output signal processor1240 and a grey scale or a binary pixel value is output representativeof the detected voltage (step 3110). A filter circuit (not shown) is aband-pass filter that filters the output voltage to detect an outputvoltage signal in a passband centered about a frequency of approximately30 MHz. The grey scale or binary pixel value is output to memorycontroller 1260 for storage in image memory 1270. In one example, theoutput grey scale or binary pixel value is stored in an address in imagememory 1270 that corresponds to the detected pixel.

In step 3112, a check is made to determine if the scan is complete. Inother words, a check is made to determine whether each pixel in the500.times.400 sensor array 1220 has been scanned and a correspondingoutput value has been stored and accumulated in image memory 1270. Ifthe scan is complete, then the routine ends. A signal or otherindication can then be generated and output from device 1200 toindicate, for example, that a fingerprint image has been successfullycaptured. If the scan is not complete, then the piezo film sensor array1220 is switched to detect the next pixel or next group of pixels (step3114). Control then returns to perform steps 3104 through 3112 at thenext pixel or next group of pixels.

As described above, piezo film sensor array 1220 can be switched bymultiplexers 1225 to detect voltage values at a single pixel or a groupof pixels. In general, any pattern for scanning pixels can be used. Forexample, a raster scan of pixels can be performed. Pixels can be scannedrow by row or column by column.

In one preferred example, when multiple groups of pixels are read out ata given instant, each pixel in a group of pixels are separated by apredetermined distance. In this way interfering effects from the ringdown oscillation in neighboring pixels are minimized or avoided. In oneexample, pixels detected in a given cycle are separated by a minimumdistance of at least 8 pixels. In this way any ring down oscillationsbetween neighboring pixels are attenuated significantly.

Example Applications of the Invention

Biometric Capture Device

FIG. 32 illustrates a biometric device 3202 according to an embodimentof the invention. Device 3202 has a sensor array 3204 according to theinvention. Device 3202 is particularly adapted for obtaining and storingfingerprint data according to the invention. Device 3202 is intended,for example, to be used by law enforcement personnel.

Mobile Biometric Capture Device

FIG. 33 illustrates a mobile biometric device 3300 according to anembodiment of the invention. Device 3300 has a sensor array 3302according to the invention at one end of the device, and a handle 3306at an opposite end. The circuitry of the device is located in a portion3304 of the device. Device 3300 is battery operated. Device 3300 is alsointended, for example, to be used by law enforcement personnel.

Wireless Transceiver Biometric Device

FIG. 34 illustrates a wireless transceiver biometric device 3400according to an embodiment of the invention. Device 3400 is intended tobe used by the general populace, for example, as an electronic signaturedevice.

Device 3400 has a sensor 3402 for obtaining biometric data, such as afingerprint, according to the invention. Device 3400 is shown as havingthree indicator lights 3404 for communication information to a user.

FIG. 35 illustrates a more detailed view of the wireless transceiverbiometric device 3400. As can be seen in FIG. 35, sensor 3402 is poweredby a battery 3504. Device 3400 has an antenna 3502 that can be used forsending information to and receiving information from other device.Device 3400 can be made to be compatible with BLUETOOTH wirelesstechnology. A key ring 3506 can be attached to device 3400. Asillustrated by FIGS. 36 and 37, device 3400 has a multitude of possibleuses.

Electronic Sales and/or Transactions

FIG. 36 illustrates using the wireless transceiver biometric device 3400to complete an electronic sales transaction. In step 1 of thetransaction, device 3400 is used to obtain a fingerprint of theindividual wanting to make a purchase. Device 3400 then transmits thefingerprint to a device coupled to cash register 3602 (step 2), whichsends the fingerprint to a third party verification service 3604 (step3). The third party verification service uses the received fingerprintto verify the identity of the purchaser (step 4) by matching thereceived fingerprint to fingerprint data stored in a database. Theidentity of the purchaser can then be sent to cash register 3602 (step5) and to a credit card service 3606 (step 6). The credit card serviceuses the data from the third party verification service to approve salesinformation received from cash register 3602 (step 7) and to prevent theunauthorized use of a credit card. Once cash register 3602 receiveverification of the purchaser's identity and verification that thepurchaser is authorized to use the credit card service, cash register3602 can notify device 3400 to send a credit card number (step 8). Cashregister 3602 can then send the credit card number to the credit cardservice 3606 (step 9), which then transfers money to the sellers bankaccount (step 10) to complete the sales transactions. These steps areillustrative of how device 3400 can be used as an electronic signaturedevice, and are not intended to limit the present invention.

Other Wireless Transceiver Biometric Device Applications

FIG. 37 illustrates other applications for which the wirelesstransceiver biometric device 3400 is well suited. For example, device3400 can be used for: building access control; law enforcement;electronic commerce; financial transaction security; tracking employeetime and attendance; controlling access to legal, personnel, and/ormedical records; transportation security; e-mail signatures; controllinguse of credit cards and ATM cards; file security; computer networksecurity; alarm control; and identification, recognition, andverification of individuals. These are just a few of the many usefulapplication of device 3400 in particular, and the present invention ingeneral. Additional applications for device 3400 and the invention willbe apparent to those skilled in the relevant arts given the descriptionof the invention herein.

Personal Area Network Applications

As described herein, embodiments of the invention are capable ofinteracting with other devices as part of a personal area network. FIG.38 illustrates one embodiment of a wireless transceiver biometric device3800 according to the invention. Device 3800 comprises a biometricdevice similar to device 1200, described above, a DSP chip 3802, aBLUETOOTH chip 3804, a display 3806, and a battery 3808. As describedabove, device 1200 has a piezo ceramic sensor array 700 and fourmultiplexers 1225 according to the invention.

Biometric device 1200 is coupled to a DSP 3802. DSP 3802 controls device1200 and stores biometric data. DSP 3802 is also coupled to BLUETOOTHchip 3804 for sending and receiving data. A display 3806 is used tocommunicate information to a user of device 3800. Device 3800 is poweredby a battery 3808. As would be known to a person skilled in the relevantart, BLUETOOTH is an agreement that governs the protocols and hardwarefor a short-range wireless communications technology. The invention isnot limited to implementing only the BLUETOOTH technology. Otherwireless protocols and hardware can also be used.

Wireless transceiver biometric device 3800 enables an individual to bein communication with compatible devices within about 30 feet of device3800. Device 3800 can connect, for example, with to telephones, cellphones, personal computers, printers, gas pumps, cash registers,Automated teller machines, door locks, automobiles, et cetera. Becausedevice 3800 can connect to and exchange information or data with anycompatible device within a personal area network, or piconet, device3800 is able to supply a standardized secure identification orauthorization token to any device, or for any process or transactionthat needs or requests it.

Public Service Layer Applications

The present invention provides a “public services layer” (PSL) high upin a BLUETOOTH stack. The PSL layer rationalizes identification andaccess control for BLUETOOTH devices communicatively coupled to eachother. In embodiments, the PSL layer supports authorization andidentification based on a fingerprint biometric signal provided by afingerprint scanner. In one example, a wireless transceiver biometricdevice 3800 can be used with a BLUETOOTH module including a BLUETOOTHprotocol stack to provide the fingerprint biometric signal. See, e.g.,the description of BLUETOOTH module, protocol stack, and compliantdevices by Jennifer Bray and Charles Sturman, Bluetooth™. Connectwithout Cables, Prentice-Hall, Upper Saddle River, N.J. 2001 (entirebook incorporated in its entirety herein by reference), and Brent Millerand Chatschik Bisdikian, Bluetooth Revealed, Prentice-Hall, Upper SaddleRiver, N.J. 2001 (entire book incorporated in its entirety herein byreference).

In embodiments, the PSL layer functionality is defined by a protocol(also called a specification). The PSL layer interprets simple requestsfrom devices in the piconet and acknowledges back with capabilities andlevel of capability in a predefined form. Vendors of BLUETOOTHappliances can add services in the PSL layer of the present invention toenhance the features of their product.

The PSL layer, which would in most cases act transparently to the normalfunction of the device until a PSL request was broadcast that requestedone of the functionality groups that the device supported. One minimumlevel of support re-broadcasts an unsatisfied request in the aid ofextending the scatter net to eventually find a device with the requestedfunction. In this way, other devices outside of the range of arequesting device can be contacted to fulfill the PSL request.

FIG. 39 is a diagram of an example piconet 3900 coupling BLUETOOTHdevices 3910, 39200 according to the present invention. Device BLUETOOTHis a fingerprint scanner with a public service layer and BLUETOOTH stackor chipset. The public service layer can support authorization andidentification. Device 3920 is any BLUETOOTH appliance. Device 3920includes a PSL layer and BLUETOOTH stack or chipset. Piconet 3900 caninclude any number of BLUETOOTH devices within the area of the piconet,within a scattemet, or coupled to the piconet through othercommunication links.

Completing a task may require many functions to be performed in concertamong a constellation of distributed BLUETOOTH appliances. The userwould have to purchase and install sufficient appliances to cover allthe functions in a task. The PSL scheme enables efficiency and costsavings as the appliances would be shared amongst users and in somecases providing multiple uses.

One example operation of the PSL layer is physical access control. A PSLlayer of wireless transceiver biometric device 3920 sends or broadcastsone or more request access signals. Such request access signals in thePSL layer can include a request for extract/match/access and datarepresentative of detected fingerprint from outside the securedperimeter via BLUETOOTH. The PSL layer in a Desktop PC with BLUETOOTHinside the secured area receives the request from the wirelesstransceiver biometric device 3920 for extract/match/access and matchesthe print data to the personnel database which could be stored in aserver and sends an access granted to the door. The BLUETOOTH door lockthen opens and the task is completed.

The savings are illustrated by: using a desktop PC that is used forother purposes, to perform the function of access control, time andattendance, personnel tracking and security. The only dedicated hardwareis the BLUETOOTH door lock as the PC and the wireless transceiverbiometric device 3800 are used for other tasks. The installation cost isminimal and the convenience of record keeping and data base managementis also minimal. The three appliances involved in this task could bepurchased from different vendors who have only communicated to the PSLstandard. The function of fingerprint extract/match/access could bepattern, minutiae, local or central or even changed at any time forgreater security and convenience etc, without effecting the door lock orwireless transceiver biometric devices 3800. The turning off or on ofsay lights, air conditioners, telephones, could all be added to thistask if desired.

Another advantage in savings is obsolescence. A building fitted withBLUETOOTH door locks, BLUETOOTH air-conditioning, BLUETOOTH smokedetectors, BLUETOOTH lighting etc. could be upgraded with biometriccontrols without installation costs.

Appliances such a smoke alarms and light fixtures can act as alarms andextend piconets into scatter nets that will bridge gaps in parks,gardens and car parks adding security and functionality to gates inremote areas.

Telephones could be marketed with BLUETOOTH PSL functionality meaningthat they can dial 911 if an emergency code is received. BLUETOOTH PSLcould signify functionality to be programmed to dial a specific numberfor private emergency services.

Protocols could be defined which log events in a FIFO so false alarmscould be traced and minimized.

In one embodiment, the PSL Specification has the elements identifiedbelow.

A decimal filing system is included. A request is broadcast for afunction that can be as specific as the number of decimal places in therequest. In this way a manufacturer can keep the task in hisconstellation of devices if the devices are available as is expected. Ifthe request is not serviced by the exact function number (FN) requiredthe next nearest FN in the scatter net is used. Clusters of FN are usedaround areas of development. For example, a light fixture can have a FNof 551.263, which indicates 500 a facility utility, 550 a light, 551 aplug in, 551.2 a table lamp, 551.26 a halogen low voltage, 551.263 madeby a person or company (not exclusive). A request for this specificfunction of turning on 551.263 may be serviced by 557.789 a wall neon asthat is all that is available at the time and the numerically nearestnumber though limited to the group of 55X lighting. The FN 551.26 can bedefined in the PSL specification, digits after this are for manufacturesuses and may be registered. In this way a lighting manufacturer maysupply software for a PC that orchestrates visual effects.

A requesting device or a PSL manager (Piconet Master Device) couldarbitrate in the scatter net to match requests and functions.

The PSL can also define the structure of how functions are allocated. AFN allows one to negotiate with vendors of door locks with minimaleffort. The PSL also gives manufacturers of other appliances insightinto task implementation where a wireless transceiver biometric device3800 could play key roles.

Function Numbers in the PSL are grouped for request and functionsuitability in one example as:

100 Emergency

200 Communications

300 Security

400 Positional

500 Facilities and Utilities

600 Entertainment

700 Computation and Information

800 Transportation

900 Miscellaneous

Sub-functional Groups are defined in one example as follows:

210 Internet connection (for transfer of credentials to local DB)

310 Personal identification via PIN

311 Personal identification via Signature

312 Personal identification via Fingerprint

313 Personal identification via Voice

314 Personal identification via Face

315 Personal identification via Eye

342 Fingerprint Feature Extraction Matching

520 Door Locks

550 Lighting

Requests and Events can also be used in the PSL specification.

Off/ON/More/Less are universal requests. User specific requests wouldnot be in the specification. Events such as ACK, NAC, can also be addedin the PSL specification.

Protocols or the structure of the request and acknowledgment include thefollowing features broadcasted in a packet.

(a) PSL indicates this packet is a PSL function request.

(b) FUNCTION NUMBER indicates the function requested

(c) REQUE indicates the operation to be performed (off/on, lock/unlock)

(d) KEYS authenticates rights of the packet. (e) PAYLOAD data ifapplicable

The PSL specification can but does not need to repeat the BLUETOOTHstructure of encryption, error checking et cetera.

The following series of examples serve to illustrate the PSL layer inseveral real-world applications:

Help I have fallen and I can't get up.

a) I press my BLUETOOTH alert button and emergency services arerequested.

b) A PC in the scatter net connects to the world wide web and executes acall to a contracting service supplier (a level one (preferred level)BLUETOOTH service) or in addition to or upon a failure the next leveloccurs.

c) A telephone with BLUETOOTH calls 911 or a service provider with arecorded message (a level two BLUETOOTH service) or upon a failure thenext level occurs.

d) A fire alarm with BLUETOOTH activates (a level three non preferredbut applicable BLUETOOTH service) or upon a failure the next leveloccurs.

e) A smoke detector activates is audio alarm in the hopes of attractingattention (a level four non preferred but applicable BLUETOOTH service)

f) An Automobile within the scatter net activates its horn and flashesits lights to alert personnel to an emergency situation. (a level fivenon preferred but applicable BLUETOOTH service)

I would like access to my office

a) I press my wireless transceiver biometric device 3800 wirelesstransceiver biometric device 3800.

b) The wireless transceiver biometric device 3800 requests andnegotiates fingerprint identification function from a PC with BLUETOOTHconnected to the server in the office.

c) The server then authorized the door lock with BLUETOOTH to beunlatched.

I would like to get through an airport

a) Baggage check in via kiosk with non reputable ID

b) Seat allocation and gate pass with ID at kiosk

c) Baggage claim with ID

Television programs could broadcast to BLUETOOTH TV that will addeffects to a BLUETOOTH home to assist future versions of Friday the13th.

I would like to make a sizable trade on margin.

a) I verify my identity via wireless transceiver biometric device 3800to my PC

b) The PC requests additional GPS location for the log of the tradeverification.

Other example uses will be apparent to a person skilled in the relevantart given the description of the invention herein. The public servicelayer according to the present invention can be used with any wirelesstransceiver biometric device including any type of fingerprint scanner.For example, fingerprint scanners which can be used include, but are notlimited to, silicon-based fingerprint scanners, optical fingerprintscanners, piezoelectric fingerprint scanners, piezo-film fingerprintscanners and piezo-ceramic fingerprint scanners.

Fingerprint Sensor Using Acoustic Impediography

There are several different types of Fingerprint sensor electricalsystem on the market: optical, capacitive, RF, thermal, and Infra-red(amongst others). This patent describes an electrical system for a newfingerprint sensor technology based on the principle of AcousticImpediography.

A Fingerprint sensor using Acoustic Impediography is comprised of anApplication Specific Integrated Circuit (ASIC or IC) and an array ofmechanical resonator used as sensing elements. The array of sensingelements contains multiple sensing elements arranged in rows and columnsas shown in FIG. 40.

Each sensing element is uniquely addressable by the Integrated Circuitusing transmitters and receivers inside the IC. Each row of sensingelements is connected to a single transmitter inside the IC. Inaddition, each column of sensing elements is connected to a singlereceiver inside the IC as shown in FIG. 41.

The IC uses its integrated transmitters to generate an electrical signalthat creates a mechanical oscillation of the sensing elements. Thismechanical oscillation generates an acoustic wave above and below eachsensing elements. Finger ridge and valleys will present differentacoustic load (or impedance) on the individual sensing elements.Depending on this acoustic impedance of the finger ridge and valleys onthe sensor, the acoustic wave generated by the sensing elements will bedifferent as shown in FIG. 42.

The ASIC has integrated transmitters connected to each row of the sensorarray. Each transmitter is individually controlled by a “TransmitterControl” block. This control block determines the timing of eachindividual transmitter. It also controls the amplitude of the signalgenerated by each transmitter. It is advantageous for the transmittersto generate a sinusoidal shaped signal with a frequency matching theresonant frequency of the sensing elements. Either the series or theparallel resonance (or both) of the mechanical resonator sensingelements could be used. A programmable “Phased Lock Loop” (PLL) is usedto generate the desired frequency generated the by transmitters as shownin FIG. 43.

The ASIC contains receivers connected to each column of the sensorarray. When a single transmitter is enabled, a receiver is used tomeasure the amount of current flowing through a single sensing elements.Each receiver pipeline is comprised of the following elements:

An input pin,

A current-to-voltage converter/amplifier,

A noise filter,

Signal conditioning circuits,

Adjustable gain and offset,

Analog-to-Digital Converter.

Once the analog signal has been converted to a digital signal by theAnalog-to-Digital Converter (ADC), it is stored into a data storagesystem to be processed and converted into a fingerprint image as shownin FIG. 44.

The amount of current measured by the receiver is inversely proportionalto the impedance of the individual sensing element. Which itself isproportional to the acoustic impedance of the ridge or valley on thissensing element. At the series resonant frequency the finger valleyimpedance is lower then the finger ridge impedance. And at the parallelresonant frequency, the finger ridge impedance is lower then the fingervalley impedance as shown in FIG. 45.

The current flowing through the sensing elements will buildup from thetime the transmitter is enabled, until it reaches a steady state. Thisbuildup time is due to the mechanical characteristics of the sensingelements. The impedance difference between ridge and valley will createdifferent current amplitudes in the selected sensing elements as shownin FIG. 46.

Each component in a receiver pipeline could be shared with otherreceiver pipelines. The ability to share components reduces the amountof circuitry inside the ASIC. FIG. 47 shows an example where the“Adjustable Gain and Offset”, and the “Analog-to-Digital Converter” areshared with other receivers. A multiplexer is used to switch the signalscoming from each receiver feeding the “Adjustable Gain and Offset”, andthe “Analog-to-Digital Converter”.

The multiplexer placement in the pipeline can vary depending on theapplication and performance requirements. FIG. 48 shows an example whereevery component in the pipeline except for the input pin is sharedbetween receivers.

To improve performance sample and hold circuits can be used to break thepipeline into time slices. Different sections of the receiver pipelinecan work on different sensing element data at different times. FIG. 49shows an example where “Sample and Hold” circuits are inserted betweenthe “Signal Conditioning” and “Adjustable Gain and Offset” blocks.Therefore, the section from the receiver input pin to the “SignalConditioning” block are working on the next sensor element data, whilethe section from the “Adjustable Gain and Offset” to the“Analog-to-Digital Converter” are working on the current sensor elementdata.

This concept of time slicing the receiver pipeline could be modified andexpended as shown in FIG. 50, where multiple “Sample and Holds” are usedalong the pipeline. The “electronic cloud” represents any electricalcomponent in the receiver pipeline.

FIG. 51 shows the current from the sensing elements in the receiverpipeline over time without any “Sample and Hold”.

FIG. 52 shows the current from the sensing elements in the receiverpipeline over time with the same set of “Sample and Hold” as shown inFIG. 49. One can see the overlap in time between the two sets of datafrom two different sensing elements. The amount of overlap isproportional to the amount of time it takes to sample every sensingelement in the sensor array. Which itself is proportional to the systemperformance.

CONCLUSION

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. It will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the invention as definedin the appended claims. Thus, the breadth and scope of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A sensing device, comprising: an array of sensingelements, and wherein said sensing elements operate based upon acousticimpediography principles; and wherein said sensing device is configuredto measure an acoustic impedance associated with at least one of saidsensing elements, said acoustic impedance being measured in proportionto a measured electrical impedance of one or more electrical signalsthat are passed through said at least one of said sensing elements; afirst electrical signal having a first frequency, is passed by saidsensor device through said at least one of said sensing elements, saidfirst frequency being equal to a serial resonant frequency of a circuitincluding said at least one of said sensing elements, and a secondelectrical signal having a second frequency, is passed by said sensordevice through said at least one of said sensing elements, said secondfrequency being equal to a parallel resonant frequency of a circuitincluding said at least one of said sensing elements, and where saidsensing device is configured to measure an amount of current of saidfirst electrical signal to determine a first electrical impedance, andis configured to measure an amount of current of said second electricalsignal second electrical signal to determine a second electricalimpedance, and where a said first impedance is lower for a finger valleythan a finger ridge, and where said second impedance is lower for afinger ridge than a finger valley, in order to determine an acousticalimpedance, and to detect a presence of a finger valley or finger ridgein association with said at least one of said sensing elements.
 2. Thesensing device of claim 1, wherein the sensing elements are arranged ina two dimensional array of rows and columns.
 3. The sensing device ofclaim 1 wherein the sensing device employs an Application SpecificIntegrated Circuit.
 4. The sensing device of claim 2 wherein at leastone transmitter transmits said electrical signal through at least one ofsaid rows, and at least one receiver receives said electrical signalfrom at least one of said columns.
 5. The sensing device of claim 4wherein said at least one transmitter and said at least one receiverreside within one Application Specific Integrated Circuit.
 6. Thesensing device of claim 1, wherein a sample and hold circuit is employedto process data received from one or more sensing elements.